As a technique of implementing hardware such as an optical switch, Japanese Patent Laid-Open No. 2003-57575 has proposed a mirror control device manufactured by micromachining. FIG. 1 is an exploded perspective view showing the arrangement of a mirror control device according to the first embodiment of the present invention. FIG. 2 is a sectional view of the mirror control device shown in FIG. 1. A conventional mirror control device also has the same mechanical arrangement as that of the first embodiment. The conventional mirror control device will briefly be described with reference to FIGS. 1 and 2.
In a mirror control device 100, a mirror substrate 200 having a mirror, and an electrode substrate 300 having electrodes are arranged in parallel.
The mirror substrate 200 includes a plate-shaped frame portion 210, a gimbal 220 arranged in the opening of the frame portion 210, and a mirror 230 arranged in the opening of the gimbal 220. The gimbal 220 can pivot about a gimbal pivot axis x in FIG. 1 which passes through a pair of torsion springs 211a and 211b. Similarly, the mirror 230 can pivot about a mirror pivot axis y in FIG. 1 which passes through a pair of torsion springs 221a and 221b. As a result, the mirror 230 pivots about the two axes which are perpendicular to each other.
The electrode substrate 300 includes a plate-shaped base portion 310, and a terrace-shaped projecting portion 320. Four electrodes 340a to 340d are formed on the four corners of the projecting portion 320 and the upper surface of the base portion 310 led out of the four corners. An insulating layer 311 made of, e.g., silicon oxide is formed on the surface of the base portion 310. The electrodes 340a to 340d, leads 341a to 341d, and interconnections 370 are formed on the insulating layer 311.
In the mirror control device 100, the mirror 230 is grounded. Positive driving voltages are applied to the electrodes 340a to 340d such that asymmetrical potential differences are generated between them, thereby attracting the mirror 230 by an electrostatic attraction and making it pivot in an arbitrary direction.